1. Field of the Invention
The present invention relates to an improved microorganism culturing dish, commonly referred to as a Petri dish. More particularly, the present invention is directed to a Petri dish with improved properties in respect to the ability to arrange one or more similar dishes to form a relatively stable stack of dishes, that is so structured and dimensioned as to enable a medical technician using the Petri dish to utilize the dish with increased efficiency and comfort, and has features which permit more efficient use of the media required to culture microorganisms.
Petri dishes generally consist of a bottom container for the medium which has a bottom wall and a single upstanding, cylindrical, peripheral side wall. The container is used in combination with a slightly larger lid having a top wall which merges into a downwardly extending cylindrical peripheral. The lid telescopically covers the container.
While the Petri dish is a seemingly simple product, it must meet many conflicting requirements of the manufacturer and the user. It is not uncommon that as many as a thousand Petri dishes are used by a technician in a single day. Efficient operations dictate that the technician must not have to use both hands to remove or replace the lid. Also it is common practice to work from an inverted stack of Petri dishes wherein the container is picked up with one hand, leaving the other hand free to streak a sample across a solidified media located in the bottom portion of the container.
It is also common practice for the laboratory technician to transport a stack of Petri dishes which have been inoculated from one portion of the laboratory to another. Accordingly, it is usual to provide some type of stacking restraint which prohibits sliding of the Petri dishes while they are being transported in a stack. A common practice is to provide a circumferential rib on the bottom of the container which mates with a circumferential rib of slightly larger or smaller diameter on the top of the lid of the Petri dish which is below the container in a stack. These mating ribs act to restrain movement of the Petri dish and prevent the stack from collapsing while it is being transported. Such arrangement of circumferential ribs has not been wholly satisfactory and has not completely prevented the problem of sliding while the stack of Petri dishes is carried.
A further problem is that, when solidified media is prepackaged in the bottom container, the solidified media tends to separate from the area adjacent to the junction of the side wall and the bottom wall of the bottom container during shipping and storage.
2. Prior Art
U.S. Pat. No. 4,160,700 to Boomus et al describes a Petri dish having an outwardly extending radial flange in the lid of a Petri dish to permit easy removal of the lid. The Boomus et al patent also discloses the use of a mating arrangement of circumferential ribs on the lid and container sections of the Petri dish which engage to inhibit sliding of a stack of Petri dishes. U.S. Pat. No. 3,198,713 to McCormick describes a Petri dish which is adapted to be arranged with one or more similar dishes to form a relatively stable stack of dishes. In the arrangement of the McCormick patent a plurality of open-top Petri dishes is arranged to form a stable stack wherein the base dish provides the lid for an underlying base dish. U.S. Pat. No. 3,649,463 to Buterbaugh describes a Petri dish having a bottom portion containing an outwardly extending peripheral flange provided with a plurality of inwardly extending slots. The flange is spaced upward from the bottom portion and away from the lower edge of the top portion to permit grasping of the flange by the fingers.